For reproduction, for example of oil paintings, copying offers a first choice. However, good copies require considerable expertise and a high expenditure of time so that they are expensive and, in quantity, cannot keep up with the demand of a rising cultural life. On the other hand, multicolor fine art printing, developed to a highly faithful reproduction in color and definition, does indeed yield valuable replicas. However, this is coupled with the disadvantage that the relief-like surface texture of the original is lacking which, in the case of an oil painting or a similar work of art, is also the means of expression of the artist and is even recognized as such by a lay person.
For the solution to this problem, as given in German Pat. specification No. 494 894, French patent No. 15 21 466, German printed specification 20 19 699 and German patent specification 2 352 966 were processes in which a transparent ply of gelatin and plastic, respectively, is placed on a multicolored print, faithful to the original, on the picture side. The transparent ply receives, through means of a form transferred from the original before or after placement, the relief configuration of the original surface. Actually imitated in this manner on the transparent ply is the relief-like surface configuration, however the resultant imitation does not give the same impression as in the case of the original since it is not formed by the paint as it is in the original. Thus the effect of the surface formed by the transparent ply is extraordinarily strongly dependent on the angle of observation, the lighting and the like.
These shortcomings are eliminated with processes in accordance with French Pat. No. 14 93 516 and French Pat. No. 15 48 337. These patents disclose a process for the reproduction of oil paintings or similarly surface-textured images by use of a relief form transferred from an original and a smooth thermoplastic color photo film that is imprinted corresponding to the original with the film together with a relief form being placed in fitting alignment and with the film thereafter being deformed by heating to correspond to the surface of the original. According to French Pat. No. 14 93 516, the relief form is provided with air passage holes. Then, laid over the relief form in fitting alignment is the color photo film, over which is placed a thick polystyrene foil. The thick polystyrene foil is heated to the softening temperature of the color photo film. Next, with a vacuum or negative pressure below the relief form and/or a superpressure above the polystyrene form, this latter is pressed together with the color photo film into the recesses of the relief form. In this fashion, after rehardening, the color photo film takes on the surface form of the original. The process in accordance with French Pat. No. 15 48 337 corresponds to this known process, with the exception that the color photo film is heated up by irradiation with infrared light instead of contact heating by means of a polystyrene foil, and forming is accomplished solely by vacuum below the relief form. Compared to the transparent relief surface plies obtained with the preceding described processes, the resulting color photo film relief surfaces represent an improvement. However, in the case of both processes, the force of heat acting upon the color photo film over a relatively long period of time, leads to a more or less strong change of the naturally temperature-sensitive printing inks. The reason for this lies in the fact that, principally , the polystyrene foil, but also the color photo film itself, (even though the latter is relatively thin) display a non-negligible heat capacity, thereby requiring some time until the heat transferred onto the unprinted side of the color photo film has brought the printed side to the required softening temperature. Accordingly, it takes some time before the compound picture of polystyrene foil and color photo film, which has an essentially greater heat capacity than the color photo film alone, is again cooled down to non-damaging temperatures.
The task set forth for the invention is to procure an improved procedure as compared to the state-of-the-art, wherein the actions of damaging high temperatures on the color photo film are essentially reduced. This is achieved by the process wherein the colored photo film, preferably polyvinyl chloride, capable of being dielectrically heated together with a reenforcing ply consisting of linen cloth-like webbing with a thin coating of a material capable of being dielectrically heated (preferably polyvinyl chloride) and capable of being welded to the colored photo film, wherein the coated reenforcing ply is laid on the back side of the color photo film and, during heating, the back side of the webbing portion of the reenforcing ply is acted upon by a pressure equalizing plate of closed-cell foam material which, like the relief form, consists of the material which is only negligibly heated dielectrically, such as silicone rubber.
Through means of the dielectric heating, the color photo film is simultaneously heated through its entire thickness and brought to the required softening temperature. Since only the thin coating and not the linen cloth-like webbing of the reenforcing ply is dielectrically heated, the compound picture, made up of the thin coating of the reenforcing ply and the color photo film, has a low heat capacity and, additionally, the webbing of the reenforcing ply that has remained cool takes on heat. Moreover, there results a still faster completion of the process and a greater output per unit of time. Also, a more precise metering of the heat being furnished is possible, both relative to intensity and to the actual period of duration.
In an advantageous form of embodiment of the process, the relief form utilized can, at least on its forming surfaces, be galvanically metal-plated or be structured completely of metal. In this fashion, trueness of form itself is guaranteed in the case of a high number of reproductions. Furthermore, a good and fast heat removal conduction results on the printed side of the color photo film.
The invention will be explained in more detail in the following with the aid of examples of embodiment, taking into account the drawing.